Core Data NSPredicate For Property of type Array

Question

i have this Core Data object

class Foo: NSManagedObject {

    @NSManaged var YearRange: AnyObject?  // [2000,2015]
}

i need to know if 2005 in in the range of the NSManagedObject property YearRange.

this is my fetch:

    let request :NSFetchRequest = NSFetchRequest(entityName:"Foo")

    let Predicate = NSPredicate(format: "xxx", "xxx")

    request.predicate = Predicate

    var error: NSError? = nil
    var matches: AnyObject = self.managedObjectContext!.executeFetchRequest(request, error: &error)!

    if (error == nil && matches.count > 0){

        println(matches)
    }

what is the NSPredicate format that can help me ?

Answer 1

Since CoreData does not natively support array attributes, I assume YearRange is defined as a Transformable. If that is the case, and assuming you are using a SQLLite store, you cannot use a predicate based on YearRange to filter the fetch request. (Transformables are stored in the SQL database as NSData blobs, and are only transformed back into the appropriate object types when loaded into memory. For the SQLLite store, CoreData compiles any predicate into the fetch SQL and evaluates the result in the database itself. Hence the predicate cannot be based on Transformables.)

You have two options: 1) you could fetch all the objects, and then filter them in memory, or 2) amend your model to store the YearRange as CoreData native types (ie. strings, numbers, dates, etc).

If the elements of the YearRange array represent the start and end years of a range, then I recommend the latter option, with two integer attributes: yearRangeStart and yearRangeEnd. If YearRange might contain several discrete years, then the first option is probably best.